A subject's visual attention can be tested by displaying a series of visual stimuli, to which the subject is instructed to respond. Typically, the stimuli are of two types, and the subject is instructed to respond to only one of them. Data are collected for each stimulus presented including the type of stimulus, whether or not the subject responded, and if so, how long the subject took to respond. The continuous performance attention task has been in use since the mid 50's (Rosvold et al., 1956, J. of Consulting and Clinical Psychology, 20: 343-350), with computerized versions available in the 1970's (Greenberg, 1987, 23: 279-282). The previous methods of analysis of the raw data generated from these methods have typically distilled the data into a few numbers which do not capture the subject's fluctuations in attention.
Another method for assessing the visual attention capabilities of a subject involves determining how long a particular visual stimulus must be present before a subject can detect it (U.S. Pat. No. 5,801,810). This method does not reveal the attentional state of the subject, rather, it requires the subject to be fully attentive.
Other reported methods determine a subject's intensity of focused attention, concentration, and/or interest by measuring signals naturally emanating from the brain (U.S. Pat. Nos. 5,983,129 and 5,377,100). These brainwaves vary across subjects and even within the same subject; thus, these methods do not provide a reliable, well-defined number for classifying attentional states.
A diagnostic assessment of psychological conditions can be made by conducting a sequence of continuous performance tasks where information is recorded to reflect the number of target stimuli correctly identified, the number of target stimuli missed, the number of responses to non-target stimuli, the number of non-target stimuli correctly missed, and the final interstimulus interval (U.S. Pat. No. 5,940,801). This method can be used in a clinical setting, as well as remote locations such as the home, school, or workplace. Using this method in remote locations is useful for psychological and behavioral problems that are highly stimulus-dependent and may not be manifested in a clinical environment, such as depression, anxiety, schizophrenia, addiction, eating disorders, attention deficit disorders, attention deficit and hyperactivity disorder. This method does not provide a way to classify performance into states.
The aforementioned methods do not accurately quantify a subject's attentional state. None classify a subject's behavior into specific well-defined states or examine fluctuations in attention over time.